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					                                                               9/10/2008




             Chapter 3
  The Tissue Level of Organization
                               • Group of similar cells
                                  – common embryonic
                                    origin
                                  – common function
                               • Histology
                                  – study of tissues
                               • Pathologist
                                  – looks for tissue changes
                                    that indicate disease
                                                       3-1




               4 Basic Tissues (1)
• Epithelial Tissue
  – covers surfaces because cells are in contact
  – lines hollow organs, cavities and ducts
  – forms glands when cells sink under the surface
• Connective Tissue
  –   material found between cells
  –   supports and binds structures together
  –    stores energy as fat
  –   provides immunity to disease
                                                       3-2




               4 Basic Tissues (2)

  • Muscle Tissue
       – cells shorten in length producing movement
  • Nerve Tissue
       – cells that conduct electrical signals
       – detects changes inside and outside the body
       – responds with nerve impulses



                                                       3-3




                                                                      1
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           Origin of Tissues
• Primary germ layers within the embryo
  – endoderm
  – mesoderm
  – ectoderm
• Tissue derivations
  – epithelium from all 3 germ layers
  – connective tissue & muscle from mesoderm
  – nerve tissue from ectoderm


                                                  3-4




                    Biopsy

• Removal of living tissue for microscopic
  examination
  – surgery
  – needle biopsy
• Useful for diagnosis, especially cancer
• Tissue preserved, sectioned and stained
  before microscopic viewing

                                                  3-5




               Cell Junctions

                              • Tight junctions

                              • Adherens junctions

                              • Gap junctions

                              • Desmosomes

                              • Hemidesmosomes
                                                  3-6




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 Tight Junctions

         • Watertight seal between
           cells
         • Plasma membranes fused
           with a strip of proteins
         • Common between cells
           that line GI and bladder




                                  3-7




Adherens Junctions

         • Holds epithelial cells
           together
         • Structural components
            – plaque = dense layer of
              proteins inside the cell
              membrane
            – microfilaments extend into
              cytoplasm
            – integral membrane proteins
              connect to membrane of
              other cell
                                  3-8




  Desmosomes

         • Resists cellular
           separation and cell
           disruption
         • Similar structure to
           adherens junction except
           intracellular
           intermediate filaments
           cross cytoplasm of cell
         • Cellular support of
           cardiac muscle
                                  3-9




                                                  3
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               Hemidesmosomes


                               • Half a desmosome
                               • Connect cells to
                                 extracellular material
                                   – basement membrane




                                                            3-10




                  Gap Junctions

                     • Tiny space between plasma
                       membranes of 2 cells
                     • Crossed by protein channels
                       called connexons forming fluid
                       filled tunnels
                     • Cell communication with ions &
                       small molecules
                     • Muscle and nerve impulses
                       spread from cell to cell
                         – heart and smooth muscle of gut
                                                            3-11




Epithelial Tissue -- General Features
•   Closely packed cells forming continuous sheets
•   Cells sit on basement membrane
•   Apical (upper) free surface
•   Avascular---without blood vessels
    – nutrients diffuse in from underlying connective
      tissue
• Good nerve supply
• Rapid cell division
• Covering / lining versus glandular types
                                                            3-12




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                 Basement Membrane
                                         • Basal lamina
                                             – from epithelial cells
                                             – collagen fibers
                                         • Reticular lamina
                                             – secreted by connective
                                               tissue cells
                                             – reticular fibers
                                         • holds cells to connective
                                           tissue
                                         • guide for cell migration
                                           during development
                                                                   3-13




                 Types of Epithelium

      • Covering and lining epithelium
        – epidermis of skin
        – lining of blood vessels and ducts
        – lining respiratory, reproductive, urinary & GI
          tract
      • Glandular epithelium
        – secreting portion of glands
        – thyroid, adrenal, and sweat glands
                                                                   3-14




          Classification of Epithelium
• Classified by arrangement of cells into layers
  – simple = one cell layer thick
  – stratified = many cell layers thick
  – pseudostratified = single layer of cells where all cells
    don’t reach apical surface
       • nuclei at found at different levels so it looks multilayered
• Classified by shape of surface cells
  –   squamous =flat
  –   cuboidal = cube-shaped
  –   columnar = tall column
  –   transitional = shape varies with tissue stretching
                                                                   3-15




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     Simple Squamous Epithelium




• Single layer of flat cells
   – lines blood vessels (endothelium), body cavities
     (mesothelium)
   – very thin --- controls diffusion, osmosis and filtration
   – nuclei centrally located
• Cells in direct contact with each other
                                                                    3-16




   Examples of Simple Squamous




 • Surface view of lining         • Section of intestinal
   of peritoneal cavity             showing serosa



                                                                    3-17




                                                  Introduction-Epithelium 18




                                                                                      6
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        Simple Cuboidal Epithelium




•   Single layer of cube-shaped cells viewed from the side
•   Nuclei round and centrally located
•   Lines tubes of kidney
•   Absorption or secretion
                                                               3-19




        Example of Simple Cuboidal




    • Sectional view of kidney tubules
                                                               3-20




                                             Introduction-Epithelium 21




                                                                                 7
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   Nonciliated Simple Columnar




• Single layer rectangular cells
• Unicellular glands =goblet cells secrete mucus
   – lubricate GI, respiratory, reproductive and urinary systems
• Microvilli = fingerlike cytoplasmic projections
   – for absorption in GI tract (stomach to anus)
                                                                 3-22




Ex. Nonciliated Simple Columnar




          • Section from small intestine

                                                                 3-23




                                               Introduction-Epithelium 24




                                                                                   8
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           Microvilli                         Introduction-Epithelium 25




                                              Introduction-Epithelium 26




Ciliated Simple Columnar Epithelium




  • Single layer rectangular cells with cilia
  • Mucus from goblet cells moved along by cilia
     – found in respiratory system and uterine tubes
                                                                3-27




                                                                                  9
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Ex. Ciliated Simple Columnar




     • Section of uterine tube
                                                   3-28




                                 Introduction-Epithelium 29




                                 Introduction-Epithelium 30




                                                                    10
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                                  Introduction-Epithelium 31




    Stratified Squamous Epithelium

• Several cell layers thick
• Surface cells flat
• Keratinized = surface cells
  dead and filled with keratin
   – skin (epidermis)
• Nonkeratinized = no
  keratin in moist living cells
  at surface
   – mouth, vagina
                                                    3-32




  Example of Stratified Squamous




  • Section of vagina
                                                    3-33




                                                                     11
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                                    Introduction-Epithelium 34




Papanicolaou Smear (Pap smear)


• Collect sloughed off cells of uterus and
  vaginal walls
• Detect cellular changes (precancerous
  cells)
• Annually for women over 18 or if sexually
  active


                                                      3-35




  Stratified Cuboidal Epithelium




                         • Multilayered
                         • Surface cells cuboidal
                            – rare (only found in
                              sweat gland ducts &
                              male urethra)
                                                      3-36




                                                                       12
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      Stratified Columnar Epithelium

    • Multilayered
    • Surface cells columnar
    • Rare (very large ducts & part of male urethra)




                                                              3-37




                                            Introduction-Epithelium 38




             Transitional Epithelium




• Multilayered
• Surface cells varying in shape
  from round to flat if stretched
• Lines hollow organs that
  expand from within (urinary
  bladder)
                                                              3-39




                                                                               13
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                                  Introduction-Epithelium 40
Transitional Epithelium




           Pseudostratified Columnar
                           • Single cell layer
                           • All cells attach to
                             basement membrane
                             but not all reach free
                             surface
                           • Nuclei at varying
                             depths
                           • Respiratory system,
                             male urethra &
                             epididymis

                                                    3-41




                                  Introduction-Epithelium 42




                                                                     14
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           Glandular Epithelium
• Derived from epithelial cells that sank below the
  surface during development
• Exocrine glands
  – cells that secrete---sweat, ear wax, saliva, digestive
    enzymes onto free surface of epithelial layer
  – connected to the surface by tubes (ducts)
  – unicellular glands or multicellular glands
• Endocrine glands
  – secrete hormones into the bloodstream
  – hormones help maintain homeostasis
                                                      3-43




       Structural Classification of
            Exocrine Glands
  • Unicellular are single-celled glands
     – goblet cells
  • Multicellular glands
     – branched (compound) or unbranched (simple)
     – tubular or acinar (flask-like) shape




                                                      3-44




      Examples of Simple Glands




        • Unbranched ducts = simple glands
        • Duct areas are blue
                                                      3-45




                                                                   15
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Examples of Compound Glands




  • Which is acinar? Which is tubular?

                                              3-46




 Duct of Multicellular Glands

                             • Sweat gland duct
                             • Stratified cuboidal
                               epithelium




                                              3-47




Methods of Glandular Secretion
            • Merocrine -- most glands
               – cells release their products by
                 exocytosis---saliva, digestive
                 enzymes & sweat
            • Apocrine
               – smelly sweat & milk
               – upper part of cell possibly pinches
                 off & dies (perhaps--see EM data)
            • Holocrine -- oil gland
               – whole cells die & rupture to
                 release their products      3-48




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                Connective Tissues
•   Cells rarely touch due to extracellular matrix
•   Matrix(fibers & ground substance secreted by cells
•   Consistency varies from liquid, gel to solid
•   Does not occur on free surface
•   Good nerve & blood supply except cartilage &
    tendons




                                                        3-49




                       Cell Types
• Blast type cells = retain ability to divide & produce
  matrix (fibroblasts, chondroblasts, & osteoblasts)
• Cyte type cells = mature cell that can not divide or
  produce matrix (chondrocytes & osteocytes)
• Macrophages develop from monocytes
    – engulf bacteria & debris by phagocytosis
• Plasma cells develop from B lymphocytes
    – produce antibodies that fight against foreign substances
• Mast cells produce histamine that dilate small BV
• Adipocytes (fat cells) store fat              3-50




 Connective Tissue Ground Substance
     • Supports the cells and fibers
     • Helps determine the consistency of the matrix
        – fluid, gel or solid
     • Contains many large molecules
        – hyaluronic acid is thick, viscous and slippery
        – condroitin sulfate is jellylike substance providing
          support
        – adhesion proteins (fibronectin) binds collagen
          fibers to ground substance

                                                        3-51




                                                                       17
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 Types of Connective Tissue Fibers
• Collagen (25% of protein in your body)
  – tough, resistant to pull, yet pliable
  – formed from the protein collagen
• Elastin (lungs, blood vessels, ear cartilage)
  – smaller diameter fibers formed from protein elastin
    surrounded by glycoprotein (fibrillin)
  – can stretch up to 150% of relaxed length and return to
    original shape
• Reticular (spleen and lymph nodes)
  – thin, branched fibers that form framework of organs
  – formed from protein collagen                   3-52




             Marfan Syndrome

 • Inherited disorder of fibrillin gene
 • Abnormal development of elastic fibers
 • Tendency to be tall with very long legs,
   arms, fingers and toes
 • Life-threatening weakening of aorta may
   lead to rupture


                                                    3-53




    Embryonic Connective Tissue:
           Mesenchyme




 • Irregularly shaped cells
 • In semifluid ground substance with reticular fibers
 • Gives rise to all other types of connective tissue
                                                    3-54




                                                                   18
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  Embryonic Connective Tissue:
   Mucous Connective Tissue




 • Star-shaped cells in jelly-like ground substance
 • Found only in umbilical cord

                                                  3-55




     Mature Connective Tissue

    •   Loose connective tissue
    •   Dense connective tissue
    •   Cartilage
    •   Bone
    •   Blood
    •   Lymph


                                                  3-56




     Loose Connective Tissues

• Loosely woven fibers throughout tissues
• Types of loose connective tissue
  – areolar connective tissue
  – adipose tissue
  – reticular tissue




                                                  3-57




                                                               19
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         Areolar Connective Tissue




• Cell types = fibroblasts, plasma cells, macrophages, mast
  cells and a few white blood cells
• All 3 types of fibers present
• Gelatinous ground substance
                                                     3-58




        Areolar Connective Tissue




               • Black = elastic fibers,
               • Pink = collagen fibers
               • Nuclei are mostly fibroblasts       3-59




                 Adipose Tissue




  •   Peripheral nuclei due to large fat storage droplet
  •   Deeper layer of skin, organ padding, yellow marrow
  •   Reduces heat loss, energy storage, protection
  •   Brown fat found in infants has more blood vessels and
      mitochondria and responsible for heat generation
                                                     3-60




                                                                    20
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                                      Fibrous Connective 61
                                                  Tissue




                                      Fibrous Connective 62
                                                  Tissue




Liposuction or Suction Lipectomy

• Suctioning removal of subcutaneous fat for
  body contouring
• Dangers include fat emboli, infection, injury
  to internal organs and excessive pain




                                                   3-63




                                                                    21
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       Reticular Connective Tissue




• Network of fibers & cells that produce framework of organ
• Holds organ together (liver, spleen, lymph nodes, bone
  marrow)
                                                          3-64




                                             Fibrous Connective 65
                                                         Tissue




                                             Fibrous Connective 66
                                                         Tissue




                                                                           22
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         Dense Connective Tissue

      • More fibers present but fewer cells
      • Types of dense connective tissue
         – dense regular connective tissue
         – dense irregular connective tissue
         – elastic connective tissue




                                                            3-67




   Dense Regular Connective Tissue




• Collagen fibers in parallel bundles with fibroblasts between
  bundles of collagen fibers
• White, tough and pliable when unstained (forms tendons)
• Also known as white fibrous connective tissue
                                                            3-68




                                               Fibrous Connective 69
                                                           Tissue




                                                                             23
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                                             Fibrous Connective 70
                                                         Tissue




 Dense Irregular Connective Tissue




• Collagen fibers are irregularly arranged (interwoven)
• Tissue can resist tension from any direction
• Very tough tissue -- white of eyeball, dermis of skin
                                                          3-71




                                             Fibrous Connective 72
                                                         Tissue




                                                                           24
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                                          Fibrous Connective 73
                                                      Tissue




                                          Fibrous Connective 74
                                                      Tissue




      Elastic Connective Tissue




• Branching elastic fibers and fibroblasts
• Can stretch & still return to original shape
• Lung tissue, vocal cords, ligament between vertebrae
                                                       3-75




                                                                        25
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         Elastic Connective Tissue




                                      Fibrous Connective 76
                                                  Tissue




                    Cartilage

• Network of fibers in rubbery ground substance
• Resilient and can endure more stress than
  loose or dense connective tissue
• Types of cartilage
  – hyaline cartilage
  – fibrocartilage
  – elastic cartilage


                                                    3-77




                                        Skeletal System 1 78




                                                                     26
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                   Hyaline Cartilage




•   Bluish-shiny white rubbery substance
•   Chondrocytes sit in spaces called lacunae
•   No blood vessels or nerves so repair is very slow
•   Reduces friction at joints as articular cartilage
                                                              3-79




                                                  Skeletal System 1 80




                                                  Skeletal System 1 81




                                                                               27
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               Fibrocartilage




• Many more collagen fibers causes rigidity & stiffness
• Strongest type of cartilage (intervertebral discs)
                                                   3-82




             Elastic Cartilage




• Elastic fibers help maintain shape after deformations
• Ear, nose, vocal cartilages
                                                   3-83




        Bone (Osseous) Tissue
• Spongy bone
   – sponge-like with spaces and trabeculae
   – trabeculae = struts of bone surrounded by red bone
     marrow
   – no osteons (cellular organization)
• Compact bone
   – solid, dense bone
   – basic unit of structure is osteon (haversian system)
• Protects, provides for movement, stores
  minerals, site of blood cell formation
                                                   3-84




                                                                  28
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                  Compact Bone




   • Osteon = lamellae (rings) of mineralized matrix
      – calcium & phosphate---give it its hardness
      – interwoven collagen fibers provide strength
   • Osteocytes in spaces (lacunae) in between lamellae
   • Canaliculi (tiny canals) connect cell to cell
                                                      3-85




                          Blood




• Connective tissue with a liquid matrix = the plasma
• Cell types = red blood cells (erythrocytes), white blood
  cells (leukocytes) and cell fragments called platelets
• Provide clotting, immune functions, carry O2 and CO2
                                                      3-86




                         Lymph

  • Interstitial fluid being transported in
    lymphatic vessels
  • Contains less protein than plasma
  • Move cells and substances (lipids) from one
    part of the body to another




                                                      3-87




                                                                   29
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                   Membranes

  • Epithelial layer sitting on a thin layer of
    connective tissue (lamina propria)
  • Types of membranes
    –   mucous membrane
    –   serous membrane
    –   synovial membrane
    –   cutaneous membrane (skin)


                                                  3-88




            Mucous Membranes

  • Lines a body cavity that opens to the outside
    – mouth, vagina, anus etc
  • Epithelial cells form a barrier to microbes
  • Tight junctions between cells
  • Mucous is secreted from underlying glands
    to keep surface moist


                                                  3-89




             Serous Membranes

• Simple squamous cells overlying loose CT layer
• Squamous cells secrete slippery fluid
• Lines a body cavity that does not open to the
  outside such as chest or abdominal cavity
• Examples
  – pleura, peritoneum and pericardium
  – membrane on walls of cavity = parietal layer
  – membrane over organs in cavity = visceral layer

                                                  3-90




                                                               30
                                                         9/10/2008




          Synovial Membranes

• Line joint cavities of all freely movable
  joints
• No epithelial cells---just special cells that
  secrete slippery fluid




                                                  3-91




                    Muscle

   • Cells that shorten
   • Provide us with motion, posture and heat
   • Types of muscle
      – skeletal muscle
      – cardiac muscle
      – smooth muscle




                                                  3-92




             Skeletal Muscle




• Cells are long cylinders with many peripheral nuclei
• Visible light and dark banding (looks striated)
• Voluntary or conscious control
                                                  3-93




                                                               31
                                                                     9/10/2008




                       Cardiac Muscle




• Cells are branched cylinders with one central nuclei
• Involuntary and striated
• Attached to and communicate with each other by
  intercalated discs and desmosomes                    3-94




                        Smooth Muscle




  • Spindle shaped cells with a single central nuclei
  • Walls of hollow organs (blood vessels, GI tract, bladder)
  • Involuntary and nonstriated
                                                              3-95




                           Nerve Tissue




 • Cell types -- nerve cells and neuroglial (supporting) cells
 • Nerve cell structure
    – nucleus & long cell processes conduct nerve signals
        • dendrite --- signal travels towards the cell body
        • axon ---- signal travels away from cell body        3-96




                                                                           32
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Systemic Lupus Erythematosus (SLE)

 •   Autoimmune disorder -- causes unknown
 •   Chronic inflammation of connective tissue
 •   Nonwhite women during childbearing years
 •   Females 9:1 (1 in 2000 individuals)
 •   Painful joints, ulcers, loss of hair, fever
 •   Life-threatening if inflammation occurs in
     major organs --- liver, kidney, heart, brain,
     etc.
                                                3-97




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